Synthetic Studies on Schisandra nortriterpenoids. Stereocontrolled Synthesis of Enantiopure C-5-<i>epi</i> ABC Ring Systems of Micrandilactone A and Lancifodilactone G Using RCM
作者:Soumitra Maity、Kiran Matcha、Subrata Ghosh
DOI:10.1021/jo1006448
日期:2010.6.18
the spiro-dihydrofuran 25. The ketal unit in 25 was then converted into the carbinols 28 and 36. A bromonium ion initiated highly stereocontrolled intramolecular etherification in 28 and 37 led to the tricyclic ethers 29 and 38, respectively. Reductive removal of bromine from 29 and 38 followed by RuO4 oxidation led to the furo-furanone derivatives 31 and 40, the C-5-epi ABC ring systems of the schisandra
已经开发出一种立体控制的方法,用于构建蜜二内酯A和lancifodilactone G的ABC环系统。该合成涉及通过由已知的d-甘露糖醇衍生的不饱和酯12制备的二烯醇14的RCM构建对映体纯的官能化的环庚烯衍生物17。在环庚烯衍生物17转变为环庚酮20的过程中,观察到氢硼化期间环庚烯衍生物17具有显着的区域选择性。由20立体选择性地制备的二烯24的RCM给出了螺二氢呋喃25。25中的缩酮单位然后被转化为甲醇28和36。溴离子在28和37中引发高度立体控制的分子内醚化,分别导致三环醚29和38。从29和38中还原去除溴,然后进行RuO 4氧化,产生了呋喃呋喃酮衍生物31和40,以及五味子降冰片五萜1和2的C-5- epi ABC环系统。